Firefox

Certainly possible but I'm sure the odds are astronomically low. After I saw this happen 3 times I started refreshing every minute and each time there was a change, both counts had increased, and this happened 8 times in a row. I could see a distribution happening of something like a vote up at minute 2, vote down at minute 3 vote up at minute 12, vote down at minute 20, etc, but this was - vote up and vote down at minute 5, same thing at minute 11, same thing at minute 16, etc, 8 times concurrently (the minutes listed here are an example, I wasn't tracking exact time between events).